In magnetic disc storage devices, information is stored on a magnetic disc by changing the magnetic moments of a series of localized areas on the disc. Typically, the localized areas are organized as concentric tracks. To store or read information from the disc, a slider, which floats above the spinning disc, is positioned over the disc so that a head within the slider may read or write information to the disc. The slider is moved to different tracks across the disc by an actuator arm that is pivotally connected to the disc drive. The actuator arm is moved by an electromagnetic actuator formed by a current carrying conductive ring and two magnetic pole pieces. The conductive ring resides on the end of the actuator arm opposite the slider and is centered between the two pole pieces. A current passing through the conductive ring creates a magnetic field that interacts with the magnetic field created by the two pole pieces, causing the actuator arm to deflect, thereby moving the slider in an arc over the surface of the disc.
In order to achieve predictable and consistent actuator arm movement, the magnetic poles must be magnetized so that they produce a particular magnetic field. In particular, each magnetic pole in a particular line of disc drives must create the same magnetic field.
To ensure that the poles produce the proper magnetic field, a sampling of magnetic poles must be tested during the production of the disc drives. This testing involves placing each magnetic pole in a flux tester that measures the amount of magnetic flux generated by the pole. In general, such flux testers place a circuit loop adjacent the magnetic pole so that the circuit loop generally surrounds all of the magnetic flux produced by the magnetic pole. The circuit loop is then moved relative to the magnetic pole such that the circuit loop cuts through the flux lines created by the magnetic pole. Movement of the circuit loop through the flux lines creates a voltage in the circuit loop that is related to the magnetic flux density (weber/meter.sup.2) produced by the pole piece and the speed at which the loop cuts through the flux lines. If this voltage is integrated relative to time, the amount of flux produced by the magnetic pole is obtained.
To provide consistent flux readings, the circuit loop must pass through each magnetic pole's flux lines in the same manner. To improve the consistency of the circuit loop's movement relative to the magnetic pole, prior art flux testers use a large number of elements that each need to be precisely manufactured. These elements are connected together by drilling holes in the elements and screwing the elements together. Although these testers eliminate some unwanted variations in the testing process, they still permit unacceptable amounts of variation in the movement of the circuit loop relative to the magnetic pole. In addition, each of the holes in the testers creates a location where dirt can accumulate.
The accumulation of dirt is undesirable since the testers are designed to be used in a clean room. In order for any apparatus to be placed in a clean room, the apparatus must be cleaned to remove any particles larger than 0.5 microns. In particular, everything that enters the clean room must be cleaned to remove magnetically charged particles that are larger than 0.5 microns. If these magnetically charged particles enter the clean room, it is possible for them to enter the disc drive being manufactured in the clean room. Such magnetic contamination can damage the disc by causing magnetic erasure of the data found on the disc.
In addition to being difficult to clean, the large number of elements found in the prior art are expensive to manufacture. As such the testers of the prior art are unacceptably expensive.
The present invention provides a solution to this and other problems, and offers other advantages over the prior art.